Abstract

A substrate step technique has been used to fabricate superconducting NbN weak links of length ∼750 Å, width ∼1.5 μm. The film in the weak‐link region is less than 100 Å thick, and shows evidence of being granular. These devices have very high resistance (as much as 30 Ω), are quite rugged, and show almost ideal Josephson response to microwave radiation at 70 GHz. A vortexflow model is expected to apply because of the small coherence length in the weak‐link material. However, the well‐known resistively shunted junction model is found to be a significantly better predictor of device behavior.